Initial flight cycle tests/research

Trying to figure out exactly how we can pull off the flock of crows in the first scene, I've been spending some more time looking at the flight cycles of birds and how that might fit into the perspective that we're aiming for. I've located some amazingly helpful resources and tons of reference videos that should hopefully serve to help us to figure out the motion of the crows.

There's this fantastic guide to bird flight written by Brendan Body that goes really in-depth into the mechanics of it and how that applies to animation. He was also kind enough to include masses of videos of birds in flight from all sorts of angles and speeds so that you can really analyse and see the movement and timing of every limb.

I thought it would probably be a better idea to get the hang of a general flight cycle from just one angle — say the front or the side — and fully understand that before even attempting to start injecting perspective into it, so I started looking at some general reference images combined with some of the videos from the above link and just sketching out a few of the poses, trying to figure out how the wing would look at each stage of movement.

I did some extremely crude and scribbles of what appeared to be the main positions of the cycle — keyframes, to some extent, I guess — the 'up' position, the mid position, and the furthest down position. I started thinking about the timings at this stage — the downstroke is slower than the upstroke due to wind/air resistance, depending on the size of the bird in question — so I tried to roughly plot out how many frames it might take each way. Crows are fairly small so probably around 6 - 7 frames to go all the way down and 4 - 5 to come back up? Tried to also think a bit about 'breaking' the limbs a bit to give them some flexibility.

On account of the fact that it was such a quick, rubbish drawing, I'm not surprised it didn't animate properly. I'm not going to try and make excuses for it, the limbs are just too stiff and the spacing is too uniform so it's just a straight up-down movement. It would certainly be fixable; slowing in/out of the upmost and downmost positions would certainly help, but it seems I was in a hideously impatient mood today and just wanted things to magically be brilliant and perfect first time. Blagh.

I had a little look at a very nice little guide on Youtube to see if I could better understand where I might be going wrong in terms of the spacing:

(The body's up/down movement is atrocious — I apologise, but I animated it in Photoshop (which has no onion skinning), so I just opted to make it bob around in a uniform manner and it looks really stupid. Should have left it.)

I referenced completely shamelessly copied the example front cycle from the video — sketching out the shapes simplified like this, I feel, did help me to better understand the underlying movement of the wing beneath the muscle and feathers. It made me realise that, previously, I'd neglected to consider the wing's individual joints and how flexible it actually is. Part of the reason it looked so stiff before, I think, is because it was a simple mass of straight lines and balls. Nothing even remotely organic about it. Wings are very flexible, and even at this rough stage I should be thinking about bending and flexing them to help loosen things up.

As nice as the referenced cycle is, it seems as if the wing stops at the top very suddenly — as if it hits an invisible ceiling. Might be nice to pad that out a bit — as well as delaying the wing at the peak of the up/down strokes.

The two videos above — both taken from Brendan Body's tutorial — are fantastic examples of the joint rotation in a bird's flight. You can clearly see how the bird tucks the tips of its wings back on the upstroke to decrease wind resistance (hence why it's faster!) It really helps to understand how, exactly, a bird gets its wing from A to B — not at all a simple up-down movement like you would expect.

The second video also highlights the delay in the bird's joints — to compare the wing to an arm, the forearm and hand continue to travel forward as the shoulder moves up. Much like the human arm in a walk cycle, in fact!

I think I'm slowly beginning to understand how this kind of thing works, but I still need a lot more practice. Hopefully I can tackle a few more basic flight cycles and really familiarise myself with the motion. Continuing to think of the wing as an arm and comparing the delay/breaking of joints with that seen in a walk cycle will probably help immensely and make the whole process seem just a little bit less alien.

To conclude: birds are weird.